Review by: Do-Lenh, Son (2009-02-17)

As opposed to traditional displays, interactive surfaces, i. e. displays that allow users to directly interact with the surface by hands or input devices and see the visual feedback, provide a more intuitive and natural form of interaction, facilitating face-to-face collaboration. This article provides a broad overview of research on horizontal interactive surfaces (aka. tabletops). The article presents several challenges that tabletop designers and researchers have to take into account and technological solutions that the authors have developed in various projects. Those challenges include: [i] Tabletop content orientation: [/i]While sitting around an interactive tabletop, multiple users do not necessarily share a common viewing orientation. As a result, visual feedbacks on the tabletop (including images and texts) need to be oriented appropriately so that each user can have the best possible view of the digital contents.

[i]Occlusion and reach. [/i]Users' hands usually obscure the digital objects that she is manipulating, and on a large tabletop a user cannot touch digital objects that are far from her reach. Researchers may use some techniques that are proposed in the paper. One technique, for example, suggests automatically enlarging digital objects when the fingers get close to them, thus decreasing occlusion.

[i]Registration and gesture reuse. [/i] How to register a hand gesture to a specific command in the tabletop application. How to reuse a defined gesture for other operations.

[i]Legacy application support. [/i] How to allow gesture-based applications on a tabletop to communicate with traditional mouse-based applications.

[i]Group interaction techniques. [/i]How to facilitate group collaboration around the tabletop. For example, the authors suggested that multi-users can replicate an application’s global menu bar for their own use. They can work with this local menu bar without the need of moving the global menu bar around the table, thereby interrupting other members’ actions in the group.

[i]Walk-up and walk-away usage issues. [/i] How to make copy of digital documents with the tabletop. The so-called "UniTable" solution lets users bring their own laptops and other mobile devices, directly connecting to the tabletop to share, manipulate, and exchange data.

Apart from these technological issues, the authors also observe how tabletop design and configuration influences user performance. An important conclusion is that tabletop surfaces are not suitable for pixel-accurate interactions (e. g. image editing). Another note suggests that in collaborative settings, tabletop applications should provide audio feedback after a user’s action. This audio feedback can facilitate either the individual or the group awareness of the collaborative task, but not both. Because the tabletop is both, a display and a direct input device, it provides a direct-touch interaction metaphor that presents remarkable challenges, including special manipulation techniques that transcend traditional mouse- and keyboard-based designs. The lessons learned from the article are valuable to the field of tabletop research, suggesting potential design and research implications for future research.